Powder metallurgy composite cam sheet and preparation method thereof

ABSTRACT

According to the invention, there are disclosed a power metallurgy composite cam sheet and a fabrication method thereof. The power metallurgy composite cam sheet is constructed by combining a power metallurgy cam be composited on a surface of a matrix. The fabrication method of the power metallurgy composite cam sheet includes sinter welding, braze welding, argon arc welding, laser welding, hot pressing and other methods. The powder metallurgy composite cam sheet fabricated by the invention has merits of stable size, good impact toughness, good abrasion resistance, low cost and so on, so that it can replace an integral cam sheet that is currently fabricated by forging, drawing, power metallurgy or other process. It is suitable for the case where a hollow camshaft is prepared by mechanical assembly, hydraulic forming, welding or other process, so that the usage requirements of an assembled camshaft can be met.

FIELD OF THE INVENTION

The present invention relates to the technical field of powder metallurgy, and particularly, to a powder metallurgy composite cam sheet and a preparation method thereof.

BACKGROUND OF THE INVENTION

Assembled camshafts have advantages of light weight, flexible design and processing, good abrasion resistance and so on, and have been widely used in engines for automobile and motorcycle. Conventional cam sheets are produced generally by adopting forging, extrusion, drawing or other processes, and then are subjected to a surface quenching treatment. A steel piece is hot forged to be a blank directly by using forging process, and then is subjected to cold forging so as to fabricate a cam sheet with a high dimensional accuracy. Cold forging can be used to prepare a cam sheet directly as well. It is also possible that extrusion process is directly used to fabricate a cam sheet, and then cold drawing is perfoimed on it for size control, so that a cam sheet with a very high dimensional accuracy is obtained. Besides, people have developed a method in which a steel tube is adopted for preparation of a cam sheet by way of cold drawing directly. The above processes have shortcomings such as high production cost, difficult adjustment for the composition of the material, etc.

As regards a cam sheet that is fabricated by using conventional power metallurgy for the sake of reducing the cost, it tends to crack upon assembly due to its drawbacks of low density, poor impact toughness, etc. In order to ameliorate the above shortcomings of the power metallurgy cam sheet, researchers perform hot forging on the power metallurgy cam sheet to further enhance its density, reduce its porosity, and improve impact toughness, and then perform quenching on the surface, so that a power metallurgy cam sheet satisfying usage requirements is attained. The above process has shortcomings of relatively high production cost and so on.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a powder metallurgy composite cam sheet and a fabrication method thereof, aiming at shortcomings in prior art.

The power metallurgy composite cam sheet provided by the invention is characterized in that, the power metallurgy composite cam sheet is constructed by combining a power metallurgy on a surface of a matrix.

The matrix in the power metallurgy composite cam sheet may be a circular tube or a special-shaped tube with a thickness ranged from 0.1-20 mm that is made of steel, nickel, titanium, copper, aluminum or other material.

The power metallurgy cam in the power metallurgy composite cam sheet may be of an iron-based powder metallurgy material, a titanium-based power metallurgy material, a nickel-based power metallurgy material, a hard alloy, or the like. Its thickness may be in the range of 0.5-50 mm.

The fabrication method of the power metallurgy composite cam sheet includes sinter welding, braze welding, argon arc welding, laser welding, hot pressing and so on, which will be described as follows, respectively.

(1) A powder metallurgy cam pressed compact is fabricated by using a conventional powder pressing method, assembled with the matrix, and then subjected to sinter welding under such process conditions that the temperature is in the range of 600-1500° C. and the time is in the range of 10-120 minutes, the atmosphere for the sinter welding being an atmosphere of hydrogen gas, decomposed ammonia, vacuum, or the like, to be fabricated into a powder metallurgy composite cam sheet.

(2) A powder metallurgy cam pressed compact is fabricated by using a conventional powder pressing method, a blank for a powder metallurgy cam sheet is fabricated by it under such process conditions that the temperature is in the range of 600-1500° C. and the time is in the range of 10-120 minutes, and then a matrix and the powder metallurgy cam are welded together by using braze welding, argon arc welding, laser welding or other process, so as to fabricate a powder metallurgy composite cam sheet. Where, material for the solder may be copper, a copper alloy, nickel, a nickel alloy, aluminum, an aluminum alloy, titanium, a titanium alloy, or the like, and morphology of the solder may be powder-shaped, wire-shaped, piece-shaped, or the like. It is carried out in an atmosphere of vacuum, hydrogen gas, decomposed ammonia, or the like, the temperature being in the range of 600-1200° C., and the time being in the range of 10-120 minutes.

(3) A matrix is placed on a core rod, and after powders are filled, it is pressed to be fabricated into a composite cam sheet compact. Then, it is subjected to sinter welding under such process conditions that the temperature is in the range of 600-1500° C. and the time is in the range of 10-120 minutes, to be fabricated into a power metallurgy composite cam sheet.

(4) Matrix powders and cam powders are placed in layers into a mold by way of filling, and then are pressed to be fabricated into a composite cam sheet compact. At last, it is sintered at 600-1500° C. for 10 to 120 minutes, to be fabricated into a powder metallurgy composite cam sheet.

(5) A matrix is placed on a core rod, and after powders are filled, it is hot pressed at 500-1400° C. for 10 to 120 minutes, to be fabricated into a powder metallurgy composite cam sheet.

(6) It is possible that matrix powders and cam powders are placed in layers into a mold by way of filling, and then are hot pressed at 500-1400° C. for 10 to 120 minutes, to be fabricated into a powder metallurgy composite cam sheet.

The invention has the following beneficial effects: the powder metallurgy composite cam sheet fabricated by the invention has merits of stable size, good impact toughness, good abrasion resistance, low cost and so on, so that it can replace an integral cam sheet that is currently fabricated by forging, drawing, power metallurgy or other process. It is suitable for the case where a hollow camshaft is prepared by mechanical assembly, hydraulic forming, welding or other process, so that the usage requirements of an assembled camshaft can be met.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structurally schematic view illustrating a power metallurgy composite cam sheet according to the invention.

Reference numerals in the FIGURE: 1 denotes the power metallurgy composite cam sheet; 11 denotes a matrix; and 12 denotes a cam.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the invention, there are proposed a powder metallurgy composite cam sheet and a fabrication method thereof, which includes powder metallurgy, sinter welding, braze welding, argon arc welding, laser welding, hot pressing and other methods. In the structurally schematic view illustrating a power metallurgy composite cam sheet that is shown in FIG. 1, a powder metallurgy cam 12 is combining on a matrix 11. Hereinafter, the invention will be described further by giving exemplary embodiments. However, they are not used to limit the invention in any way.

Embodiment 1

A 45# steel pipe of Ø20×3×13 mm is subjected to surface sand blasting for rust removal, degreasing, cleaning and other treatment. A cam sheet green compact having an inner hole of Ø20.1×5×13 mm (with a top part of 37.3 mm) is produced with mixed powders having chemical compositions of Fe—Cr—Mo—Si—P—C by pressing at 600 MPa, and then, the steel pipe and the cam sheet green compact are assembled together, and subjected to sinter welding at a temperature of 1120° C., in H₂ atmosphere for 30 minutes, so that a power metallurgy composite cam sheet is fabricated.

Embodiment 2

A cam sheet green compact having an inner hole of Ø25.3×3×13 mm (with a top part of 37.3 mm) is produced with mixed powders having chemical compositions of Fe—Cr—Mo—Si—P—C by pressing at 600 MPa, and then, it is subjected to sintering at a temperature of 1120° C., in H₂ atmosphere for 30 minutes, so that a power metallurgy cam sheet is fabricated. A 45# steel pipe of Ø25×2×13 mm is subjected to surface sand blasting for rust removal, degreasing, cleaning and other treatment, and then, the steel pipe and the powder metallurgy cam sheet are assembled together with a copper foil placed therebetween, and subjected to welding at a temperature of 1115° C., in decomposed ammonia atmosphere for 20 minutes, so that a power metallurgy composite cam sheet is fabricated.

Embodiment 3

A cam sheet compact having an inner hole of Ø25.3×3×13 mm (with a top part of 37.3 mm) is produced with mixed powders having chemical compositions of Fe—Cr—Mo—Si—P—C by pressing at 600 MPa, and then, it is subjected to sintering at a temperature of 1120° C., in H₂ atmosphere for 30 minutes, so that a power metallurgy cam sheet is fabricated. A 45# steel pipe of Ø25×2×13 mm is subjected to surface sand blasting for rust removal, degreasing, cleaning and other treatment, and then, the steel pipe and the powder metallurgy cam sheet are assembled together, and fabricated to be a powder metallurgy composite cam sheet by way of laser welding.

Embodiment 4

A cam sheet having an inner hole of Ø35.3×3×20 mm (with a top part of 50 mm) is produced with the use of a hard alloy of YG12(WC_Co12) by processing. A 45# steel pipe of Ø35×4×20 mm is subjected to surface sand blasting for rust removal, degreasing, cleaning and other treatment, and then, the steel pipe and the powder metallurgy cam sheet are assembled together with a AgCu28 solder of 0.03 mm placed therebetween, and subjected to braze welding at a temperature ranged from 820-850° C., under vacuum for 20 minutes, so that a power metallurgy composite cam sheet is fabricated.

The foregoing are merely preferable embodiments of the invention, but the protection scope of the invention is not limited thereto. All changes or replacements, as would be obvious to those skilled in the art within the technical scope disclosed by the invention, shall be embraced in the protection scope of the invention. Therefore, the protection scope of the invention shall be defined by protection scope of claims. 

1-10. (canceled)
 11. A power metallurgy composite cam sheet, wherein, the power metallurgy composite cam sheet is constructed by combining a power metallurgy cam on a surface of a matrix, a thickness of the matrix is in a range of 0.1-20 mm, and a thickness of the powder metallurgy cam in the powder metallurgy composite cam sheet is in a range of 0.5-50 mm.
 12. The composite cam sheet according to claim 11, wherein, the matrix in the power metallurgy composite cam sheet is a circular tube or a special-shaped tube made of steel, nickel, titanium, copper, or aluminum.
 13. The composite cam sheet according to claim 11, wherein, the power metallurgy cam in the power metallurgy composite cam sheet is of an iron-based powder metallurgy material, a titanium-based power metallurgy material, a nickel-based power metallurgy material or a hard alloy.
 14. A fabrication method of a power metallurgy composite cam sheet, comprising the following step: combining a power metallurgy cam on a surface of a matrix so as to form the power metallurgy composite cam sheet.
 15. The fabrication method of the power metallurgy composite cam sheet according to claim 14, wherein the step of combining a power metallurgy cam on a surface of a matrix comprises the following steps: fabricating a pressed compact for the powder metallurgy cam by using a conventional powder pressing method, fabricating a blank for the powder metallurgy cam sheet at a temperature is in the range of 600-1500° C. for 10-120 minutes, and then welding the matrix and the powder metallurgy cam together by using braze welding, argon arc welding, or laser welding, wherein, material for a solder may be copper, a copper alloy, nickel, a nickel alloy, aluminum, an aluminum alloy, titanium, or a titanium alloy, and its morphology is powder-shaped, wire-shaped, or piece-shaped, the welding is carried out in an atmosphere of vacuum, hydrogen gas, decomposed ammonia, or other protective atmosphere at a temperature in a range of 600-1200° C. for 10-120 minutes.
 16. The fabrication method of the power metallurgy composite cam sheet according to claim 14, wherein the step of combining a power metallurgy cam on a surface of a matrix comprises the following steps: placing a matrix on a core rod, and after powders are filled, pressing the powders into a composite cam sheet pressed compact, next, sinter welding the pressed compact at a temperature is in a range of 600-1500° C. for 10-120 minutes.
 17. The fabrication method of the power metallurgy composite cam sheet according to claim 14, wherein the step of combining a power metallurgy cam on a surface of a matrix comprises the following steps: placing matrix powders and cam powders in layers into a mold by way of filling, then pressing the powders into a pressed compact for the composite cam sheet, and lastly, sintering the pressed compact at 600-1500° C. for 10 to 120 minutes.
 18. The fabrication method of the power metallurgy composite cam sheet according to claim 14, wherein the step of combining a power metallurgy cam on a surface of a matrix comprises the following steps: placing a matrix on a core rod, and after powders are filled, hot pressing the powders at 600-1400° C. for 10 to 120 minutes.
 19. The fabrication method of the power metallurgy composite cam sheet according to claim 14, wherein the step of combining a power metallurgy cam on a surface of a matrix comprises the following steps: placing matrix powders and cam powders in layers into a mold by way of filling, and then hot pressing the powders at 500-1400° C. for 10 to 120 minutes
 20. The fabrication method of the power metallurgy composite cam sheet according to claim 14, wherein the step of combining a power metallurgy cam on a surface of a matrix comprises the following steps: fabricating a pressed compact for the powder metallurgy cam by using a conventional powder pressing method, assembling it with the matrix, and then sinter welding the pressed compact assembled with the matrix at a temperature is in a range of 600-1500° C. for 10-120 minutes, the atmosphere for the sinter welding being an atmosphere of hydrogen gas, an atmosphere of decomposed ammonia or vacuum.
 21. The fabrication method of the power metallurgy composite cam sheet according to claim 14, wherein, the matrix in the power metallurgy composite cam sheet is a circular tube or a special-shaped tube made of steel, nickel, titanium, copper, or aluminum.
 22. The fabrication method of the power metallurgy composite cam sheet according to claim 14, the power metallurgy cam in the power metallurgy composite cam sheet is of an iron-based powder metallurgy material, a titanium-based power metallurgy material, a nickel-based power metallurgy material or a hard alloy.
 23. The fabrication method of the power metallurgy composite cam sheet according to claim 14, a thickness of the matrix is in a range of 0.1-20 mm, and a thickness of the powder metallurgy cam in the powder metallurgy composite cam sheet is in a range of 0.5-50 mm. 